Strong interface-induced spin-orbit coupling in graphene on WS2

TL;DR

This study demonstrates that placing graphene on WS2 substrates significantly enhances its spin-orbit coupling, leading to potential new topological states, confirmed by experimental measurements and first-principles calculations.

Contribution

It reveals a strong interface-induced spin-orbit interaction in graphene on WS2, a novel finding that opens pathways for engineering topological states.

Findings

Spin-relaxation time in graphene on WS2 is 2-3 orders of magnitude smaller than on SiO2 or hBN.

Enhanced spin-orbit interaction causes a pronounced weak anti-localization effect.

First-principles calculations confirm strong SOI and provide a low-energy effective Hamiltonian.

Abstract

Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.